Active production quad 2:1 multiplexer
The SN74HC258D: In an outdoor telecom or factory-floor controller that sees 70°C ambient inside the enclosure, the die still has 15°C of headroom before the rated ceiling.
Housed in a 16-SOIC (0.154", 3.90mm width) surface-mount package with a 1.27mm pitch. The supplier device package is 16-SOIC, a standard JEDEC outline that places without tombstoning risk on a typical reflow profile. No exposed pad means the thermal path is through the leads only — keep the ambient below 85°C or derate the output current. Supplied in tube packaging. The tube orientation is end-to-end with the pin 1 index at the same end — a pick-and-place feeder changeover between tubes takes one cycle if the tube is loaded correctly.
Output drive and signal integrity
Each output sources or sinks 7.8mA typical at the rated supply voltage. This is enough to drive one or two standard 74HC inputs directly, but a fan-out of more than four loads will stretch the rise time beyond the 6ns typical — buffer the output for a bus with eight receivers. A single independent circuit with four 2:1 multiplexer channels shares a common output enable and select line. The select-to-output propagation delay is typically 15ns at 5V, 50pF load — fast enough for a 20 MHz clock domain but not for a 50 MHz bus without pipeline registers.